The discovery that ultra-high purity glass fibers are efficient and effective transmitters of light signals over long distances has stimulated a broad and sophisticated technology. The glass fiber waveguide itself, as a transmission medium, has become a standard commodity, in much the same way as copper wires became in an earlier generation, but the methods and systems for interconnecting fiber waveguides continue to evolve. Glass fiber interconnection techniques are significantly more demanding than copper wire connectors due in part to the requirement that glass fibers must be connected end to end, and connected with a precision sufficient to exactly align very small fiber waveguide cores to within a few microns, and often within a fraction of a micron. Because fiber waveguides are capable of carrying enormous quantities of information, relative to copper wires, fiber waveguide cables to date typically require only a relatively few number of fibers to match or even exceed the capacity of large bundles of wires in copper cables. However, with the increasing capacity demanded by current and future data and multimedia transmission networks, the number of fibers in a single transmission cable continues to grow.
The end to end high precision connection requirement of fiber waveguides precludes simply bundling of large numbers of individual fibers in a cable as was the practice with copper wires. Instead the multiple fibers are organized in a high precision, fixed, spatial relation. A common approach for such arrays are ribbon cables in which a plurality of fibers are organized and molded side by side in a plastic ribbon. Connectors used to interconnect these ribbons are typically made of metal or silicon plates in which high precision v-grooves are etched with high precision parallel grooves. The fibers are placed side by side in one such grooved bottom plate and another mating v-groove plate is placed over the top of the linear array. The top and bottom plates of the connector are assembled together with clamps or an adhesive.
While ribbon connectors are capable of very high transmission capacities there is a need for even greater capacity. An approach for addressing this is to stack fiber waveguide ribbons. The interconnection for such stacked arrays requires a similarly stacked connector, which presents new problems in precisely aligning the fiber waveguides in the added or stacking dimension.
It has also been recognized that the use of silicon or metal plates in v-groove connectors contributes to a relatively high cost connector. Silicon was originally the material of choice since v-grooves can be formed in silicon with high precision and reliability using crystallographic etch techniques. Significant cost reductions have been proposed by substituting relatively inexpensive plastic materials for silicon. However, there is no corresponding crystallographic etch mechanism if a plastic material is used. The proposals anticipated that v-groove connector parts could be molded or extruded using dimensionally stable plastic materials, and these would provide adequate precision for the connector. These proposals have been successfully implemented, but precision in the alignment of fibers remains an issue, especially as the size and complexity of the connectors grows.